Linear slide mechanism for an extendable rearview mirror for vehicles

ABSTRACT

An extensible outside rearview mirror for a vehicle includes a spring-clamped slide mechanism that ensures a zero clearance fit between sliding components to avoid vibration. Bearing members between the sliding components reduce friction and provide a consistent reaction force to ensure smooth operation of an actuator mechanism which extends or retracts the mirror assembly along a support arm. The slide mechanism includes V-shaped guiderails vertically aligned with opposing V-shaped guiderails on the mounting bracket assembly. Rod-like bearing means are interposed between the opposing guiderail pairs. A cantilever clamp jaw with spring means biases one guiderail toward the other with a high spring force which provides superior rigidity and thus enhanced mirror image clarity.

Priority based upon provisional application Ser. No. 60/283,753 filed onApr. 16, 2001, entitled “Linear Slide Mechanism for an ExtendableRearview Mirror for Vehicles” is hereby claimed.

FIELD OF THE INVENTION

The present invention relates to a rearview mirror for a vehicle whichis extendable toward or away from the vehicle laterally to selectivelyprovide different viewing positions as desired, for example when thevehicle is towing a trailer or the like.

BACKGROUND OF THE INVENTION

It is known to provide vehicles with extendable rearview mirrors whichextend selectively from the vehicle body along a support arm whichextends laterally from the body of the vehicle. This type of extendablemirror is shown for example in U.S. Pat. No. 5,572,376 issued to Pace.The Pace mirror further includes a rack gear drive and a flexible bootwhich provides a cover between the vehicle and the motor housing toprotect portions of the apparatus from exposure. A problem with thisprior art device, however, is that the slidable components of thesub-assembly and support arm produce wear of the parts, thus creatingundesirable movement in the slide assembly which produces excessivevibration in the mirror assembly resulting in poor vision through themirror. It is known to use plate springs such as shown in theabove-captioned U.S. patent to Pace to take up clearances between slidecomponents of the extension arm mechanism however, because of thelimited space between these parts, the practical use of this type ofspring provides a spring force which is relatively weak in relation tothe reaction forces created by the mass of the mirror sub-components.

Another extendable rearview mirror for a vehicle is disclosed in U.S.Pat. No. 6,116,743 issued to Hock. The mirror assembly of the Hockdevice includes a bracket which is slidable around a support arm andincludes internal spring means for taking up the gap between the outersurface of the support arm and the inner surface of the bracket. Thisdevice is a complex assembly of many small parts including screws andother fasteners. U.S. Pat. No. 5,969,860 issued to Whitehead shows anextendable mirror which slides along longitudinal rails located on theoutside of the mirror housing. Hence the rails are not protected fromthe adverse elements of the weather.

There is therefore a need in the art for an extensible rearview mirrorsupport mechanism which is resistant to wear and which remains extremelystable and vibration-resistant throughout the entire stroke of itsmotion. It is further desired to provide a mechanism which is easilyassembled to allow high volume manufacturing. For yet further economy ofmanufacture there is a need to provide a “no-tool assembly” of parts.

SUMMARY OF THE INVENTION

In order to solve the needs in the art explained above, the presentinvention provides an extendable rearview mirror for a vehicle whichprovides a spring-clamped slide mechanism that ensures a zero tolerancefit between sliding components to avoid vibration. It further includesbearing members between the sliding components to reduce friction andprovide a consistent reaction force to ensure smooth operation of theactuator mechanism. This type of mirror is particularly useful insituations where the vehicle is towing something behind it and enhancedrearward vision is provided by positioning the rearview mirror to itsfully-extended position.

The superior functional characteristics of the present invention areprovided by a unique support bar clamp mechanism which slidably affixesthe rearview mirror housing and other components of the rearview mirrorassembly to the support arm. The sliding movement is achieved withaccurate slidable engagement of the mirror assembly along the supportarm through the full extent of its longitudinal movement. This structureincludes unique upper and lower V-shaped guide rails which face opposingV-shaped guide rails on the mounting bracket assembly. Rod-like bearingmeans are interposed between the bracket guide rails and the support armguide rails to engage the mounting bracket and the support arm againstmovement in any direction except along the longitudinal axis of thesupport arm.

To achieve a sufficient amount of clamp force, the bracket assemblyincludes a cantilever clamp jaw which also includes the lower bracketguide rail. The clamp jaw is pivotal about a fulcrum and is biasedtoward clamping engagement with the support arm by spring means which isoperative between a mirror sub-assembly mounting bracket and the leverarm of the clamp jaw which extends to the opposite side of the mountingbracket. Because of the shape of modern rearview mirror housings that isdictated by aesthetic considerations, there is a large void in thehousing behind the mirror assembly mounting bracket. Since the springmeans of the present invention is behind the bracket and positioned inthis void, a single, large spring with a high spring force can be used.This high spring force provided by the present invention contributessignificantly to the superior rigidity of the present design compared tothe prior art. Support arm clamp force may be further increased by themechanical leverage provided by the clamp jaw lever arm.

In one embodiment of the invention the bearing rods are composed of anablatable material which leaves deposits on the support arm guide railsas it is used. These material deposits act as a filler to smooth oversurface irregularities of the guide rails which may be present ifinexpensive casting methods are used to form the rails. In this way, therespective bearing surfaces are increased in area as the bearings “wearin”. This occurs rapidly since the unit surface pressure between thebearing material and the guide rails is initially very high due to thevery small point of contact between the cylindrical outer surface of therod and the flat surfaces of the V-shaped rails. When the slidemechanism is operated, the material of the bearing rods is quicklyremoved from the rods and deposited along the surface of the support armrails until a point of equilibrium is reached between the surfacefriction and the increase in bearing surface area. Once this wear-inpoint is reached, a consistent and low coefficient of surface frictionis maintained.

More specifically, the applicants have invented an extendable rearviewmirror assembly for a vehicle which includes a rotatable support arm forattachment to a vehicle body. A mirror assembly is mounted on thesupport arm and includes a bracket and a surrounding housing affixedthereto. A mirror sub-assembly including a mirror glass, support plate,and motor-driven positioning means is affixed to a first side of thebracket and lies within the housing. The assembly includes clamp meanswith jaws on the bracket for slidably affixing the bracket to thesupport arm. A first clamp jaw is adjacent the top of the housing andstationary with respect to the bracket and engages a first guide raillocated along a top of the support arm. A second movable clamp jaw isadjacent the bottom of the housing and includes pivot means to forceablyengage a second guide rail located along a bottom of the support arm.The first and second jaws define a substantially vertical clamping planebetween them which lies along the first side of the bracket. The mirrorassembly also includes a first bearing means interposed between thefirst jaw and first guide rail and a second bearing means interposedbetween the second jaw and the second guide rail. Both bearing means areelongate, rod-shaped members composed of solid PFTE, a substantiallyablatable material, such that initial operation of the slide mechanismcauses the bearing means to deposit friction-reducing material upon thesurfaces of the guide rails. The first and second jaws each include aguide rail and face opposite their respective support arm guide rails.All guide rails further include surfaces which have a V-shapedcross-section. The movable clamp jaw includes force-applying springmeans urging the second jaw in a direction of clamping and is movable toa point of release where the bracket is laterally releasable from thesupport arm. The second clamp jaw moves by way of a lever arm having afirst end which engages the coil-type compression spring means andextends to an opposite side of the bracket. The bracket has a fulcrumabout which the lever arm pivots. The fulcrum is on a bottom supportplate of the bracket which holds the spring and the second jaw in theiroperative positions solely by the co-mutual compression of engagedparts. The spring operates between the end of the lever arm and anabutment both being located on the opposite side of the bracket. Theaggregate center of mass of all components is adjacent the plane ofclamping.

The assembly also comprises a support arm having a mounting bracketaffixed to it in slidable engagement. The clamp means on the bracketincludes two jaws each engaging top and bottom edges of the support armrespectively, the clamp means including a movable jaw which pivots on alever arm extending from the bracket such that the movable jaw forceablyengages a bearing surface along one of the edges of the support arm. Thebracket is slidably affixed to the support arm on only one side suchthat when the jaw is moved to a point of release, the jaws of the clampmeans are laterally releasable from the edges of the support arm.

The low friction of the slide assembly of the present invention isbeneficial in that it requires a lower actuator force which contributesto the lower power consumption, low noise, and longer life of theactuator motor and drive system which may be any suitable screw orgear-drive system known in the art. The invention achieves all of theseattributes while rigidly restricting movement along all axes of motionexcept the longitudinal axis of the support arm. The rigidity of thesystem is further enhanced by employing guide rails which are verticallyspaced a greater distance apart than other known internal slideassemblies. This provides wide-track stability in the vertical plane andthus torsional vibration is mitigated and stable reflected visionthrough the mirror plate is achieved. Other objects and advantages ofthe present invention will be apparent from the following drawings anddescription of the preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded perspective view of a rearview mirror unitwhich employs the slide assembly of the present invention.

FIG. 2 is a partial view of FIG. 1 showing the main componentsrepresenting the slide mechanism of the present invention.

FIG. 3 is a side sectional view of the completed assembly of parts shownin FIG. 1.

FIG. 4 is a top rear isometric view of the slide assembly of the presentinvention.

FIGS. 5a and 5 b are side sectional views of the bearing and guide railpoints of engagement showing the initial surface contact points beforeand after break-in respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an exploded assembly view of the presentinvention including all major components of the rearview mirror areshown. A mirror sub-assembly 11 comprises a mirror glass support andmotor driven positioning elements fitted to the bracket assembly 13which includes support arm 17 that is attached to a vehicle body bracket(not shown) preferably by rotatable mount 10 at one end of the arm. Thebracket of the slide assembly is affixed to housing 15 that includes anaperture 16 through which the support arm 17 extends. The assembly mayfurther include an extensible-contractible flexible boot 19 to protectthe support arm from exposure.

Referring now to FIG. 2, the preferred embodiment of the slide mechanismof the present invention includes bearing rods 19 which are interposedbetween the V-shaped guide rails of support arm 5 and complementaryopposing V-shaped rails on the bracket assembly. The bracket assemblyincludes bracket 3 and clamp jaw 7 which is biased toward the upperguide rail of the bracket by spring means 12 which supplies a springforce through a lever arm of the clamp jaw that extends to the oppositeside of the bracket. The bracket 3 is affixed to the mirror housing 1 bysuitable attachment means such as screws 22.

Referring now to FIG. 3, a side sectional view of the complete assemblyof components shown in FIG. 1, is depicted. Bracket assembly 13 carriesthe mirror sub-assembly 11 that includes the mirror glass, a supportplate, and motor driven positioning means. The cantilever clamp jaw 7pivots upon fulcrum 8 to forceably clamp the support arm 17 intoslidable engagement with the bracket assembly. The fulcrum 8 is locatedalong a portion of the bracket bottom support plate 35. A lever arm 9 ofthe clamp jaw extends to the opposite side of the bracket assembly andis forced downward by compression coil spring 12 that operates betweenthe end of clamp jaw lever arm 9 and bracket spring abutment 32. Bearingrods 19 are interposed between opposing V-shaped guide rails whichlaterally traverse the top and bottom edges of both the bracket assemblyand the support arm. By this construction, the support arm rails areself-centering between the bracket rails. Also, it will be readilyunderstood from the mechanical relations shown in FIG. 3 that movementof the support arm with regard to the bracket assembly will be rigidlyrestricted along all axes of motion except the longitudinal axis of thesupport arm. It will further be observed that spring means 12 will aloneretain the assembly of the parts without the need for any otherfastening means, all parts being held together in interlockingengagement by the spring force of spring 12. This provides greatlyreduced assembly time and fewer parts.

The guide rails are preferably coplanar in the vertical plane thereforeproviding great rigidity against torsion in the vertical plane.Furthermore, the bracket and support arm are preferably C-shaped so thatthe center mass of the mirror sub-assembly is close to the verticalplane defined by the guide rails and the support arm. The forwardextending (relative to the vehicle) lever arm and spring also aid inadvantageously locating the center of mass of the mirror sub-assemblyproximate to the guide rail plane. This further adds to the rigidity ofthe assembly by decreasing the torsional reaction force moment about thesupport arm axis created by vertical accelerations.

Referring now to FIG. 4, the clamp jaw lever arm and spring means isclearly depicted. Bracket 33 includes a bottom support plate 35 whichcaptively receives a projection of the cantilever clamp jaw to establisha fulcrum and point of rotation. Spring means 12 operates between theend of the clamp jaw lever arm 36 and an abutment 32. Support arm 17includes upper and lower V-shaped guide rails 38 and 39 respectively.Since coil spring 12 is not located directly between the sliding parts,it may be a large and powerful spring which can supply the desiredamount of rigidity to the slide assembly.

Referring now to FIGS. 5a and 5 b, before and after side sectional viewsof the bearing rod and guide rail contact points are shown for the uppersupport arm guide rail 38 and opposing upper bracket guide rail 20. Asdepicted in these illustrations, the bearing rods 19 deposit some oftheir material 34 along the surface of the guide rails 38 of the supportarm as the bearing rods 19 wear in. Initially, frictional points ofcontact are along lines on the surface of the bearing rods. As the slidemechanism wears in, the areas of contact 36 become planar (i.e. flatsurfaces) and thus contact area is greatly increased after break-in.This reduces the coefficient of friction between the sliding parts andprovides a uniform contact surface area between the sliding parts at allpoints along the stroke of the bracket assembly. The increase in contactsurface area also contributes to the rigidity of the mechanicalengagement between the parts. Unwanted vibration is further mitigated bythe use of a soft, ablative bearing material, of the preferred type.Such a material is solid Teflon® PFTE of the general type.

It will be understood to those of skill in the art that there may bemany modifications and adaptations of the invention other than thosespecifically described from the foregoing preferred embodiment andalternate embodiments. However, the present invention should be limitedin scope only by the following claims and their legal equivalents.

What is claimed is:
 1. An extendable rearview mirror assembly for avehicle, comprising: a support arm for attachment to a vehicle body; amirror assembly mounted on said support arm, said mirror assemblyincluding a bracket and a surrounding housing affixed thereto; a mirrorsubassembly affixed to a first side of the bracket and lying within saidhousing; and clamp means on said bracket for slidably affixing saidbracket to said support arm, comprising; a first jaw being stationarywith respect to said bracket and engaging a first guide rail locatedalong a top of said support arm; and a second, movable jaw includingpivot means, said second jaw forceably engaging a second guide raillocated along a bottom of said support arm, said first and second jawsdefining a clamping plane between them which lies along the first sideof said bracket.
 2. The mirror assembly of claim 1 wherein said clampingplane is substantially vertical.
 3. The mirror assembly of claim 1wherein said second jaw includes a guide rail and faces opposite saidsecond support arm guide rail, both guide rails further includingsurfaces which have a V-shaped cross-section.
 4. The mirror assembly ofclaim 1 wherein said second jaw includes force-applying spring meansurging said second jaw in a direction of clamping.
 5. The mirrorassembly of claim 1 wherein said mirror sub-assembly includes a mirrorglass, a support plate, and motor-driven positioning means.
 6. Themirror assembly of claim 5 wherein the second jaw is movable to a pointof release where the bracket is laterally releasable from the supportarm.
 7. The mirror assembly of claim 5 wherein the aggregate center ofmass of all components is substantially in the clamping plane.
 8. Themirror assembly of claim 7 further described in that said first jaw isadjacent the top of the housing and said second jaw is adjacent thebottom of the housing.
 9. The mirror assembly of claim 7 wherein thebracket and the support arm are C-shaped.
 10. The mirror assembly ofclaim 1 further including first bearing means interposed between saidfirst jaw and said first guide rail and second bearing means interposedbetween said second jaw and said second guide rail.
 11. The mirrorassembly of claim 10 wherein said bearing means are composed of asubstantially ablatable material such that initial operation of saidslide mechanism causes said bearing means to deposit friction-reducingmaterial upon the surfaces of the guide rails.
 12. The mirror assemblyof claim 10 wherein said movable clamp jaw includes a lever arm havingan end which engages spring means, the end of said lever arm extendingto an opposite side of said bracket.
 13. The mirror assembly of claim 12wherein said bracket includes a fulcrum about which the lever armpivots.
 14. The mirror assembly of claim 13 wherein said spring is acoil-type compression spring.
 15. The mirror assembly of claim 14wherein said fulcrum is located on a bottom support plate of saidbracket which holds the spring and the second jaw in their operativepositions solely by the co-mutual compression of engaged parts.
 16. Themirror assembly of claim 14 wherein said spring operates between the endof the lever arm and an abutment both being located on the opposite sideof said bracket.
 17. The mirror assembly of claim 3 wherein said firstjaw further includes a guide rail and faces opposite said first supportarm guide rail, both guide rails further including surfaces which have aV-shaped cross-section.
 18. The mirror assembly of claim 10 wherein thefirst and second bearing means are elongate, rod-shaped members.
 19. Themirror assembly of claim 18 wherein the bearing rods extend the lengthof the guide rails on the bracket.
 20. The mirror assembly of claim 10wherein said bearing means are composed of solid PFTE.
 21. An extendablemirror assembly for a vehicle, comprising: a support arm having amounting bracket affixed thereto in slidable engagement therewith; clampmeans on said bracket including two jaws each engaging top and bottomedges of the support arm respectively, said clamp means including atleast one movable jaw which extends from a lever arm and pivots on afulcrum extending from said bracket and forceably engages a bearingsurface along one of said edges of the support arm; and said bracketslidably affixed to said support arm on only one side thereof such thatwhen said movable jaw is moved to a point of release, the jaws of saidclamp means and said bracket are laterally releasable from the edges ofsaid support arm.